DIRECT OBSERVATION OF 4F SPLITTING BETWEEN (110) SURFACE AND BULK ATOMS OF W

With large surface-sensitivity enhancement achieved by use of p-polarized light, soft-x-ray photoemission spectra of 4f core levels from the outermost atoms of the (110) face of tungsten have been observed. High-resolution spectra show two well-separated 4f lines split by 0.30 eV, with the low-binding-energy peak being assigned to surface atoms. The ratio of the intensity of the surface peak to the bulk peak as a function of photon energy exhibits striking features which are tentatively explained. © 1983 The American Physical Society.